The value of E for a system that performs 120 kJ of work on its surroundings and gains 50kJ of heat is ___?

Iknow #2 is d. i just need to know why

When balancing a chemical equation:

I'm learning about the periodic tables and what each subject's configuration is. for example, hydrogen is 1s^1, but i don't understand how you get that. can someone me understand how to figure out how to figure this out? sorry if the question makes no sense, but it would really a lot if you could me understand! you so much if you can!